Methods of manufacturing a stator core for a brushless motor

ABSTRACT

Method of manufacturing a stator core includes stacking a plurality of substantially T-shaped teeth obtained from a jigsaw pattern of said teeth into a plurality of stacks. In each said stack, said teeth are substantially aligned with each other. Said method includes winding said stacks with a plurality of windings and placing said stacks along the perimeter of a polygonal outer surface of a ferromagnetic tube having an inner channel. Each side of said outer surface corresponds to each said stack and contacts the bases of said legs of each said stack. Said method includes inserting said stacks and said tube into an inner space defined by an annular inner surface of a mold and a shaft into said channel. Said stacks are stationed along the circumference of said inner surface. Said method includes vacuum encapsulating said inner space in epoxy resin and removing said mold and shaft.

TECHNICAL FIELD

Generally, the present disclosure relates to electric motors. Moreparticularly, the present disclosure relates to methods of manufacturinga stator core.

BACKGROUND

In the present disclosure, where a document, act or item of knowledge isreferred to or discussed, this reference or discussion is not anadmission that the document, act or item of knowledge or any combinationthereof was, at the priority date, publicly available, known to thepublic, part of common general knowledge or otherwise constitutes priorart under the applicable statutory provisions; or is known to berelevant to an attempt to solve any problem with which the presentdisclosure is concerned.

Electric motors are widely used for converting electrical energy intomechanical energy. A stator is a component in a conventional permanentmagnet or electromagnet electric motor. Generally, the stator is aphased electromagnet, which, via magnetization and demagnetization,causes a rotor of the motor to rotate, thus operating the motor.Examples of electric motors include brushed motors and brushless motors.

Quality and quantity of materials used for manufacturing the stator arefactors, which often contribute to an operating efficiency of theelectric motor. Typically, soft magnetic alloys, such as compositesmanufactured under Hyperco® 50 Alloy or Vacoflux® brands, possesscharacteristics desired for stator manufacturing. Some of suchcharacteristics include a high magnetic flux density and a lowelectromagnetic hysteresis, as exemplified via a thin hysteresis loop.

Disadvantageously however, in many electric motor applications, usingsoft magnetic alloys as a primary raw material is cost-prohibitive. Aconventional stator core manufacturing process entails stamping aplurality of T-shaped stator teeth ringed in a sun-shape from thinlaminated steel sheets, stacking the rings to a desired height andmounting the ring stacks onto a shaft for subsequent winding with acoil. As a result of the stamping step, the stamped out portions aresubjected to undesired stress and the leftover portions of the sheetsremain unused and are thus wasted. Although such waste is tolerable ifthe sheets are relatively cheap, such tolerance is impractical when thesheets are expensive, sensitive to stress, brittle or delicate,especially when the sheets include soft magnetic alloys. Accordingly,there is a need to address at least one of the foregoing disadvantages.

While certain aspects of conventional technologies have been discussedto facilitate the present disclosure, no technical aspects aredisclaimed and it is contemplated that the claims may encompass one ormore of the conventional technical aspects discussed herein.

BRIEF SUMMARY

The present disclosure effectively addresses at least one of theforegoing disadvantages. However, it is contemplated that the presentdisclosure may prove useful in addressing other disadvantages in anumber of technical areas. Therefore, the claims should not necessarilybe construed as limited to addressing any of the particulardisadvantages discussed herein.

An object of an example embodiment of the present disclosure is toprovide a technology for effectively reducing waste of raw materialsused in stator core manufacturing, while effectively addressing at leastone drawback resulting from presence of stator slot gaps, increasingwinding fill ratio and reducing stator Eddy current.

An example embodiment of present disclosure is a method of manufacturinga stator core. Said method includes stacking a plurality of teeth into aplurality of stacks. Said teeth are obtained from a jigsaw pattern ofsaid teeth. Said teeth are substantially identical to each other insize. Each said tooth is substantially T-shaped as defined by two armsprotruding sideways from a leg. In each said stack, said teeth aresubstantially aligned with each other. Said method further includeswinding said stacks with a plurality of windings and placing said stacksalong the perimeter of a polygonal outer surface of a ferromagnetic tubehaving an inner channel extending therethrough. Each side of said outersurface corresponds to each said stack and contacts the bases of saidlegs of each said stack. Said method yet even further includes insertingsaid stacks and said tube into an inner space defined by an annularinner surface of a mold and a shaft into said channel. Said stacks arestationed along the circumference of said inner surface. The topsurfaces of the arms face said inner surface. Said method also includesvacuum encapsulating said inner space in an epoxy resin and removingsaid mold and said shaft.

Another example embodiment of present disclosure is a method ofmanufacturing a stator core. Said method includes stacking a pluralityof teeth into a plurality of stacks. Said teeth are obtained from ajigsaw pattern of said teeth. Said teeth are substantially identical toeach other in size. Each said tooth is substantially T-shaped as definedby two arms protruding sideways from a leg. In each said stack, saidteeth are substantially aligned with each other. Said method furtherincludes winding said stacks with a plurality of windings and placingsaid stacks along the perimeter of a polygonal inner surface of aferromagnetic tube. Said inner surface defines an inner space. Each sideof said polygonal inner surface corresponds to each said stack andcontacts the bases of said legs of each said stack. Said method evenfurther includes inserting a cylindrical shaft into said inner space.The top surfaces of the arms face said shaft. Said method also includesvacuum encapsulating said inner space in an epoxy resin and removingsaid shaft.

Yet another example embodiment of present disclosure is a method ofmanufacturing a stator core. Said method includes cutting a sheet into ajigsaw pattern of teeth substantially identical to each other in size.Each said tooth is substantially T-shaped as defined by two armsprotruding sideways from a leg. Said sheet includes a soft magneticalloy. Said method further includes stacking said teeth into a pluralityof stacks. In each said stack, said teeth are substantially aligned witheach other. Said method even further includes winding said stacks with aplurality of windings. Said method also includes either placing saidstacks along the perimeter of a polygonal outer surface of a firstferromagnetic tube having an inner channel extending therethrough,wherein each side of said outer surface corresponds to each said stackand contacts the bases of said legs of each said stack, inserting ashaft into said inner channel and said stacks and said first tube into amold inner space defined by an annular inner surface of a mold, saidstacks are stationed along the circumference of said annular innersurface, the top surfaces of the arms face said annular inner surface,vacuum encapsulating said mold inner space in a first epoxy resin andremoving said mold and said shaft, or placing said stacks along theperimeter of a polygonal inner surface of a second ferromagnetic tube,wherein said polygonal inner surface defines a tube inner space, eachside of said polygonal inner surface corresponds to each said stack andcontacts the bases of said legs of each said stack, inserting acylindrical shaft into said tube inner space, the top surfaces of thearms face said cylindrical shaft, vacuum encapsulating said tube innerspace in a second epoxy resin and removing said cylindrical shaft.

The present disclosure may be embodied in the form illustrated in theaccompanying drawings. Attention is called to the fact, however, thatthe drawings are illustrative only. Variations are contemplated as beingpart of the disclosure, limited only by the scope of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, aspects, advantages and features of thepresent disclosure will become more apparent to one skilled in the artby describing in further detail example embodiments thereof withreference to the accompanying drawings, in which:

FIG. 1 shows a perspective view of an example embodiment of a pluralityof wound stacks placed within a mold according to the presentdisclosure;

FIG. 2 shows a perspective exploded view of an example embodiment of aplurality of wound stacks placed within a mold according to the presentdisclosure;

FIG. 3 shows a perspective view of an example embodiment of a pluralityof stator teeth cut into a jigsaw pattern according to the presentdisclosure;

FIG. 4 shows a perspective view of an example embodiment of a pluralityof stator teeth wound with a winding according to the presentdisclosure; and

FIG. 5 shows a perspective view of an example embodiment of a statortooth prior to insertion into a winding according to the presentdisclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present disclosure now will be described more fully hereinafter withreference to the accompanying drawings, in which various embodiments areshown. This disclosure may, however, be embodied in many differentforms, and should not be construed as limited to the embodiments setforth herein. Rather, these embodiments are provided so that thisdisclosure will be thorough and complete, and will fully convey thescope of the disclosure to those skilled in the art. Like referencenumerals refer to like elements throughout.

It will be understood that when an element is referred to as being “on”another element, it can be directly on the other element or interveningelements may be present therebetween. In contrast, when an element isreferred to as being “directly on” another element, there are nointervening elements present. As used herein, the term “and/or” includesany and all combinations of one or more of the associated listed items.

It will be understood that, although the terms “first,” “second,”“third” etc. may be used herein to describe various elements,components, regions, layers and/or sections, these elements, components,regions, layers and/or sections should not be limited by these terms.These terms are only used to distinguish one element, component, region,layer or section from another element, component, region, layer orsection. Thus, “a first element,” “component,” “region,” “layer” or“section” discussed below could be termed a second element, component,region, layer or section without departing from the teachings herein.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting. As used herein, thesingular forms “a,” “an” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. It willbe further understood that the terms “comprises” and/or “comprising,” or“includes” and/or “including” when used in this specification, specifythe presence of stated features, regions, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, regions, integers, steps,operations, elements, components, and/or groups thereof.

Furthermore, relative terms, such as “lower” or “bottom” and “upper” or“top,” may be used herein to describe one element's relationship toanother element as illustrated in the Figures. It will be understoodthat relative terms are intended to encompass different orientations ofthe device in addition to the orientation depicted in the Figures. Forexample, if the device in one of the figures is turned over, elementsdescribed as being on the “lower” side of other elements would then beoriented on “upper” sides of the other elements. The example term“lower,” can therefore, encompasses both an orientation of “lower” and“upper,” depending on the particular orientation of the figure.Similarly, if the device in one of the figures is turned over, elementsdescribed as “below” or “beneath” other elements would then be oriented“above” the other elements. The example terms “below” or “beneath” can,therefore, encompass both an orientation of above and below.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It willbe further understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and thepresent disclosure, and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein. Allpublications, patent applications, patents, figures and other referencesmentioned herein are expressly incorporated by reference in theirentirety.

Example embodiments are described herein with reference to cross sectionillustrations that are schematic illustrations of idealized embodiments.As such, variations from the shapes of the illustrations as a result,for example, of manufacturing techniques and/or tolerances, are to beexpected. Thus, embodiments described herein should not be construed aslimited to the particular shapes of regions as illustrated herein butare to include deviations in shapes that result, for example, frommanufacturing. For example, a region illustrated or described as flatmay, typically, have rough and/or nonlinear features. Moreover, sharpangles that are illustrated may be rounded. Thus, the regionsillustrated in the figures are schematic in nature and their shapes arenot intended to illustrate the precise shape of a region and are notintended to limit the scope of the present claims.

Hereinafter, the present disclosure is further described in detail withreference to the accompanying drawings.

U.S. Pat. No. 8,267,673 is herein incorporated by reference in itsentirety.

FIG. 1 shows a perspective view of an example embodiment of a pluralityof wound stacks placed within a mold according to the presentdisclosure.

An assembly 10 includes a mold 11, a base 12, a shaft 13, a plurality ofstacks 14, a plurality of separators 15 and a ferromagnetic tube 16. Theouter surface of mold 11 is polygonal to facilitate for use with a vise.Shaft 13 is connected to base 12. Base 12 can be connected to mold 11.

FIG. 2 shows a perspective exploded view of an example embodiment of aplurality of wound stacks placed within a mold according to the presentdisclosure. Some elements of this figure are described above. Thus, samereference characters identify same or like components described aboveand any repetitive detailed description thereof will hereinafter beomitted or simplified in order to avoid complication.

Assembly 10 is used in a method of manufacturing a stator core for anelectric motor. Said method includes stacking a plurality of teeth intostacks 14. Said teeth are obtained from a jigsaw pattern of said teeth.Said teeth are substantially identical to each other in size. Each saidtooth is substantially T-shaped as defined by two arms protrudingsideways from a leg. In each stack 14, said teeth are substantiallyaligned with each other. Stacking teeth into stacks 14 facilitateselectrical insulation and allows for thicker laminations for highmagnetic material ratio.

Said method also includes winding stacks 14 with a plurality ofwindings. An example of such winding is a laminated wire. Each saidwinding corresponds to each stack 14 and loops around said legs alongthe perimeter of each stack 14. Since teeth 17 are wound from behind, noslot gap is needed. Hence, teeth 17 can be positioned in mold 11 withoutspacers. Also, such winding allows for significant reduction of statorslot harmonics, thus reducing rotor losses predominantly throughvibration and noise. In addition, winding a stator in this mannerimproves winding uniformity and increases material, such as copper, fillratio.

Said method further includes placing stacks 14 along the perimeter of apolygonal outer surface of ferromagnetic tube 16 having an inner channelextending therethrough. Said inner channel can be of any shape. Eachside of said outer surface corresponds to each stack 14 and contacts thebases of said legs of each stack 14. Tube 16 can include iron.

Said method even further includes inserting shaft 13 into said innerchannel and stacks 14 and tube 16 into an inner space defined by anannular inner surface of mold 11. Stacks 14 are stationed along thecircumference of said annular inner surface. The top surfaces of thearms face said annular inner surface.

Said method yet even further includes vacuum encapsulating said innerspace in an epoxy resin. Stacks 14 are held together via the epoxy. Saidmethod additionally includes removing mold 11 and shaft 13. Mold 11 canbe coated with a mold release agent to facilitate release of thehardened epoxy resin. Mold 11 can include aluminum or paraffin. Saidvacuum encapsulation mechanically fuses teeth 17 in place, whilemaintaining the electrically insulated properties of each phase andimproving cooling.

Said annular inner surface includes separators 15. Each separator 15 isstationed between two of stacks 14. Separators 15 extend in parallelalong said annular inner surface.

FIG. 3 shows a perspective view of an example embodiment of a pluralityof stator teeth cut into a jigsaw pattern according to the presentdisclosure. Some elements of this figure are described above. Thus, samereference characters identify same or like components described aboveand any repetitive detailed description thereof will hereinafter beomitted or simplified in order to avoid complication.

A plurality of teeth 17 is obtained from a jigsaw pattern of teeth 17.Within such pattern, teeth 17 are nested. Each tooth 17 is cutseparately and within such pattern, teeth 17 are tightly nested allowingfor little waste of manufacturing material. Teeth 17 are substantiallyidentical to each other in size. Each tooth 17 is substantially T-shapedas defined by two arms protruding sideways from a leg. Said patterndefines at least a portion of a sheet. At least one of said teethincludes a soft magnetic alloy. Said portion is formed by cutting. Saidcutting includes waterjet cutting, which minimally exposes themanufacturing material to thermal and mechanical stress. An example ofsaid soft magnetic alloy is an alloy including cobalt, iron and vanadiumof 2%. Such alloys can be manufactured under Hyperco® 50 Alloy orVacoflux® brands.

FIG. 4 shows a perspective view of an example embodiment of a pluralityof stator teeth wound with a winding according to the presentdisclosure. Some elements of this figure are described above. Thus, samereference characters identify same or like components described aboveand any repetitive detailed description thereof will hereinafter beomitted or simplified in order to avoid complication.

Stacks 14 are wound with a plurality of windings 18, such as a laminatedwire. Each winding 18 corresponds to each stack 14 and loops around saidlegs along the perimeter of each stack 14.

FIG. 5 shows a perspective view of an example embodiment of a statortooth prior to insertion into a winding according to the presentdisclosure. Some elements of this figure are described above. Thus, samereference characters identify same or like components described aboveand any repetitive detailed description thereof will hereinafter beomitted or simplified in order to avoid complication.

Teeth 17 are stacked into stacks 14. Each tooth 17 is substantiallyT-shaped as defined by two arms protruding sideways from a leg. In eachstack 14, teeth 17 are substantially aligned with each other. Stacks 14are wound with windings 18. Each winding 18 corresponds to each stack 14and loops around said legs along the perimeter of each stack 14. Atleast one of windings 18 is a coil or a belt.

As a result of the foregoing, stator core can be used with an outerrotor. Also, scrap material from which teeth are cut is effectivelyreduced. This allows for use of more powerful and expensive softmagnetic alloys, while maintaining affordability. Furthermore, eachtooth 17 is electrically insulated from each other thereby reducing Eddycurrents or core loss, thus improving efficiency/power density of anelectric motor employing such stator core. Moreover, the winding processis simplified, since each stack 14 is wound from the back allowing forless material and less resistance losses.

Using the above description and accompanying drawings, it is apparent toone skilled in the art that said method can be modified to manufactureanother type of rotor, such as an inner rotor. Accordingly, anotherexample embodiment of present disclosure is a method of manufacturing astator core. Said method includes stacking a plurality of teeth 17 intoa plurality of stacks 14. Teeth 17 are obtained from a jigsaw pattern ofteeth 17. Teeth 17 are substantially identical to each other in size.Each tooth 17 is substantially T-shaped as defined by two armsprotruding sideways from a leg. In each said stack, teeth 17 aresubstantially aligned with each other. Said method further includeswinding stacks 14 with a plurality of windings 18 and placing stacks 14along the perimeter of a polygonal inner surface of a ferromagnetictube. Said inner surface defines an inner space. Each side of saidpolygonal inner surface corresponds to each stack 14 and contacts thebases of said legs of each stack 14. Said method even further includesinserting a cylindrical shaft 13 into said inner space. The top surfacesof the arms face shaft 13. Said method also includes vacuumencapsulating said inner space in an epoxy resin and removing shaft 13.

In said method, said pattern can define at least a portion of a sheet.At least one of teeth 17 can include a soft magnetic alloy. At least oneof windings 18 can be a coil or a belt. Each winding 18 can correspondto each stack 14 and loop around said legs along the perimeter of eachstack 14. At least one of windings 18 can be laminated.

In said method, said portion can be formed by cutting. Shaft 13 caninclude a plurality of separators 15. Each separator 15 can be stationedbetween two of stacks 14.

In said method, shaft 13 can be connected to a base 12. Separators 15can extend in parallel along the length of shaft 13. Said cutting caninclude waterjet cutting.

In said method, the outer surface of said tube can be polygonal. Saidmold can include paraffin or aluminum.

In said method, stacks 14 can have a substantially identical height.

Yet another example embodiment of present disclosure is a method ofmanufacturing a stator core. Said method includes cutting a sheet into ajigsaw pattern of teeth 17 substantially identical to each other insize. Each tooth 17 is substantially T-shaped as defined by two armsprotruding sideways from a leg. Said sheet includes a soft magneticalloy. Said method further includes stacking teeth 17 into a pluralityof stacks 14. In each stack 14, teeth 17 are substantially aligned witheach other. Said method even further includes winding stacks 14 with aplurality of windings 18. Said method also includes either placingstacks 14 along the perimeter of a polygonal outer surface of a firstferromagnetic tube 16 having an inner channel extending therethrough,wherein each side of said outer surface corresponds to each stack 14 andcontacts the bases of said legs of each stack 14, inserting a shaft 13into said inner channel and stacks 14 and said tube 16 into a mold innerspace defined by an annular inner surface of a mold 11, stacks 14 arestationed along the circumference of said annular inner surface, the topsurfaces of the arms face said annular inner surface, vacuumencapsulating said mold inner space in a first epoxy resin and removingmold 11 and shaft 13, or placing stacks 14 along the perimeter of apolygonal inner surface of a second ferromagnetic tube, wherein saidpolygonal inner surface defines a tube inner space, each side of saidpolygonal inner surface corresponds to each stack 14 and contacts thebases of said legs of each stack 14, inserting a cylindrical shaft 13into said tube inner space, the top surfaces of the arms face saidcylindrical shaft 13, vacuum encapsulating said tube inner space in asecond epoxy resin and removing said cylindrical shaft 13.

In said method, said cutting can include waterjet cutting. At least oneof windings 18 can be a coil or a belt.

In said method, shaft 13 can be connected to a base 12. The outersurface of mold 11 can be polygonal.

In said method, base 12 can be connected to mold 11. Stacks 14 can havea substantially identical height.

In conclusion, herein are presented methods of manufacturing a statorcore. Embodiments of the present disclosure are illustrated by examplein the drawing figures and throughout the written description. It shouldbe understood that numerous variations are possible, while adhering tothe present disclosure without departing from the broader spirit andscope of the disclosure as set forth in the claims that follow. Suchvariations are contemplated as being a part of the present disclosure.

What is claimed is:
 1. A method of manufacturing a stator core, saidmethod comprising: stacking a plurality of teeth into a plurality ofstacks, wherein said teeth are obtained from a jigsaw pattern of saidteeth, said teeth are substantially identical to each other in size,each said tooth is substantially T-shaped as defined by two armsprotruding sideways from a leg, in each said stack said teeth aresubstantially aligned with each other; winding said stacks with aplurality of windings; placing said stacks along the perimeter of apolygonal outer surface of a ferromagnetic tube having an inner channelextending therethrough, wherein each side of said outer surfacecorresponds to each said stack and contacts the bases of said legs ofeach said stack; inserting said stacks and said tube into an inner spacedefined by an annular inner surface of a mold and a shaft into saidchannel, wherein said stacks are stationed along the circumference ofsaid inner surface, the top surfaces of the arms face said innersurface; vacuum encapsulating said inner space in an epoxy resin; andremoving said mold and said shaft.
 2. The method of claim 1, whereinsaid pattern defines at least a portion of a sheet, at least one of saidteeth includes a soft magnetic alloy, at least one of said windings is acoil or a belt and each said winding corresponds to each said stack. 3.The method of claim 2, wherein said portion is formed by cuffing, saidannular inner surface includes a plurality of separators, at least oneof said windings is laminated and each said separator is stationedbetween two of said stacks.
 4. The method of claim 3, wherein said shaftis connected to a base, said separators extend in parallel along saidannular inner surface, said cuffing includes waterjet cuffing.
 5. Themethod of claim 4, wherein the outer surface of said mold is polygonal,said mold includes paraffin or aluminum.
 6. The method of claim 5,wherein said base is connected to said mold, said stacks have asubstantially identical height.